Dr. Ellis-Davies has developed a series of new calcium cages which use the well known ortho-nitrobenzyl photochemistry for uncaging. He wishes to characterize these compounds using flash photolysis techniques and to measure the rate of appearance of the released Ca using low affinity Ca dyes (e.g. fluo-3FF or Ca-orange-5N). He developed a new photochemical protecting groups (not based on nitrobenzyl chemistry) which will be quite fast (ca. 100 ns for uncaging). These compounds will also be tested.